DETAILED DESIGN AND CONSTRUCTION OF THE FIRST UNIT OF THE FLAP GATE TYPE BREAKWATER INSTALLED ON THE SEABED

The flap gate type breakwater lays down on the seabed in normal times to secure the passage of vessels, and when a tsunami or storm surge is predicted, it floats above the water surface and closes the route to prevent inundation damage. Development of this technology was started in 2003, and after three years of actual sea area tests from 2011, it was first adopted in the tsunami countermeasure facility conducted by Iwate Prefecture in 2017. In the detailed design, we paid attention to the maintainability after the equipment was completed, and in the on-site construction, we paid attention to the construction method of the on-site joining between the bottom structure of the flap gate type breakwater and 56 steel pipe piles, which were expected to be difficult. Through a field test run, we confirmed the operating characteristics of the gate in the actual machine and confirmed that it satisfied the specified performance. Construction was completed successfully in December 2020.